1. Field of the Invention
The present invention relates to an anti-wear, high-strength, damage-resistant rail used for sharp curves of a high-axle load railroad having a highly rigid track and, more particularly, to a high-strength, damage-resistant rail of which a fitting property to wheels during an initial period of use of the rail can be improved, and resistance to damage to a head top portion can be improved.
2. Description of the Related Art
A head of a rail has a head top portion, corner portions, head side portions, and jaws. A conventional anti-wear, high-strength rail used in a track of sharp curves of a high-axle load railroad which uses wooden crossties is heat-treated such that the hardness of the corner and head side portions is equal to that of the head top portion. Therefore, the anti-wear properties of the rail corner portions are the same as those of the rail head top portion.
However, contact between the wheels and the rails is complicated, and the contact pressures vary depending on the position of the rail head-wheel contact. In a sharp curve of a high-axle load railroad, large slip forces act on a rail gauge corner portion (i.e., an inner corner portion) and rail head side surfaces. However, large contact pressures act on the rail head top portion and the rail gauge corner portion. As a result, the rail gauge corner portion and the rail head side portions of the conventional anti-wear, high-strength rail are worn much more than the rail head top portion. Therefore, the rail head top portion is always worn much less than the rail gauge corner portion, and a maximum contact pressure from each wheel acts on the central less-worn portion of the rail head top portion.
Since the contact state between the wheels and the conventional anti-wear, high-strength rail having uniform wear properties of the rail head is as described above, it takes a long period of time to fit wheels to the rail during an initial period of use of the rails. A local excessive contact stress lasts for a long period of time, and defects caused by fatigue tend to be formed. Even after the wheels are brought into satisfactory fitness to the new rails, a maximum contact pressure acts on the rail head top portion of each rail. Decisive problems are not posed in this condition when wooden crossties are used to form a track. However, when concrete crossties are used to form a highly rigid track, an impactive maximum contact pressure generated upon passing of a rolling stock is increased. Therefore, damage called the surface contact fatigue (crack) typically occurs in the central rail head top portion.
In order to prevent the head check according to a conventional technique, a method of grinding and correcting a rail head surface layer prior to accumulation of fatigue in the rails is employed. However, this operation is time-consuming and costly. In addition, it is also difficult to determine an optimal grinding/correcting time.